Source Importance Sampling
Setting up a source as a lambertian emitter can be easily done in FRED using the Detailed Source model but often ends up being inefficient for raytracing because the collection optics subtend a small solid angle compared to the emission of the source. Often, however, we can take advantage of FRED’s surface scattering property to efficiently direct rays from a source to a collector. The purpose of this knowledge base article is to describe the procedure for setting up a lambertian source which uses surface scattering to efficiently direct rays into an optical system.
Download the PDF: Source Importance Sampling
Download the FRED document: sourceImportanceSampling.frd